tvu tech episode 1 extra information
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Fundamentals of Analogue and Digital
Broadcasting
Fundamentals of Analogue and Digital
Broadcasting
BSc. Media TechnologyBSc. Media TechnologyMay 2007May 2007
BSc. Media TechnologyBSc. Media TechnologyMay 2007May 2007
Q. Is it inevitable that all broadcasting will go digital?
• The radio spectrum is a finite resource• Society today wants more choice, more
TV channels, more phones, etc.• Digital broadcasting makes more efficient
use of the available radio frequency bandwidth
Q. Is it inevitable that all broadcasting will go digital?
• Analogue TV switch off planned to start in 2007 - 2012
• Digital distribution over the Internet is breaking down all the old models of broadcasting and traditional retail
Common Terms
Analogue
Digital
Bandwidth
Compression
Define the term Analogue:
• A continuous analogy of a sound or light wave transmitted as an electrical signal, which is an alternating voltage (A/C)
• Any audio or video equipment that has analogue signals going through it
• Old equipment!
A/C signalVolts
+
- Time
Waveforms:
Sine waves Complex waves
Analogue:
• Audio signals
• Video signals
• Problems: Distortion, not robust, large bandwidth signals
1011001101001001110010010101101110100100100010010010
10010DigitalDigital
Define the term Digital:
• Represent all signals or data with binary numbers, 0 or 1
• Turns audio and video signals into discrete values, e.g. snapshot measurements of the a/c voltage waveform at regular points in time
• Is this a new technology?
PCM - Pulse Code Modulation
Voltage
Time
5 4 3 2 1 0 1 2345
+
- + 2 = (10010011), + 4 = (10010100), - 1 = (01101100)
PCM - Pulse Code Modulation
Volume
Time
Advantages:
• Robust• Can be copied and cloned • No distortion
• Can take up less bandwidth than analogue when compressed
BandwidthBandwidth
Bandwidth
• This defines the maximum amount of information we can transmit through a given channel or connection
• Could be described as how much water you can get through a pipe
Bandwidth• In analogue broadcasting this is how
much of the radio spectrum is used by the TV channel or radio station
• In digital broadcasting: How many ‘bits per second’
Electro-magnetic Radio Spectrum
30 GHzEHF
3 GHzSHF
300MHzUHF
30MHzVHF
3 MHz300 KHz30 KHz
Radio Spectrum
150 -300 KHzLong Wave
AM
500 -1600 KHzMedium Wave
AM
6 -18MHzShort Wave
AM
88 -108 MHzFM
10.7 -12.7 GHz Satellite TV
217 -230 MHzDAB radio
470 -840 MHzTerrestrial TV
1800 MHzPCN
Mobile phones
900 MHzGSM
Mobile phones
2320 - 2345S Band
Digital Radio
1470 - 1490 MHzL Band
Digital Radio
Other used frequencies:Police, emergency services, military, navigation, CB radio, toys, microphones,WiFi, Bluetooth, etc.
Bandwidth Examplesshowing bits per second
Bandwidth Examplesshowing bits per second
Modem56 kbit
ADSL4 MbitCD audio
1.4 Mbit
DVD9.6 Mbit
HDTV &DV video25 Mbit
BluRay disc54 Mbit/sec
CompressionCompression
Compression
• Digital broadcasting would not be possible without data compression
• Compression also achieves the goal of efficient use of the airwaves
• We can now fit 6 - 8 digital TV channels into the same RF bandwidth as one old analogue TV channel
Codecs
• Short for code - decode• A mathematical algorithm describing how
to reduce the size of the data• Can be a Lossless or Lossy process• Can be built into a hardware device or
software running on a computer
Codec examples:
• Video: MPEG 1, MPEG 2, DivX, Windows Media video, MPEG 4 - H.264
• Audio: MP3, ATRAC, AAC, Windows Media audio, DTS, Dolby Digital AC3, Real Audio, Ogg Vorbis, MLP lossless
• Image: JPEG, JPEG2000, PNG, Gif, • Data: Zip, Stuffit
Compression Examplesstereo audio files
Compression Examplesstereo audio files
AAC-HE48 kbit/sec
Uncompressed CD audio1.4 Mbit/sec
MiniDisc282 Kbit/sec
MP3128 Kbit/sec
Summary:
• The global society is entering the digital information age
• All media production is becoming completely digital from start to finish
• For efficiency all broadcasting is going digital
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